TPO roofing: Latest advancement in single-ply technology

Whether reroofing an existing plant or constructing a new facility, it is important to choose the roofing system that best fits the company's long-term needs.

05/01/1999


Whether reroofing an existing plant or constructing a new facility, it is important to choose the roofing system that best fits the company's long-term needs. In the past decade, the roofing decision has become more difficult as a number of technological advancements have been made to the components and performance characteristics of the products. In the single-ply flexible membrane category, thermoplastic polyolefins (TPOs) are among the newest entries into the market.

TPOs are made from a blend of polypropylene (PP) and ethylene-propylene rubber (EPR) to create a material that combines the best attributes of today's most popular single-ply membranes -- EPDM and PVC. The resulting TPO offers the weathering resistance, flexibility, and low-temperature properties of EPDM; and the heat weldability and tear, puncture, abrasion, and chemical resistance of a thermoplastic.

Several manufacturers offer TPO membranes, with each having a unique formulation. In fact, no two TPO membranes are exactly alike in physical properties, feel, or look. Some TPOs feel rubber-like and flexible, while others are more rigid.

However, TPO membranes generally exhibit strong physical-property characteristics, including resistance to UV degradation and punctures, as well as flexibility in cold temperatures. The materials also resist a wide variety of chemicals, and are suitable for direct contact with most common roofing materials. TPO membranes can be installed directly over polystyrene insulation without the need for a protection barrier.

Although the materials are not inherently fire resistant, they can be made fire and weather resistant during the manufacturing process. The TPO polymer is compounded with UV stabilizers, pigments, and a flame retardant package to yield a finished product that meets all the requirements of a single-ply system.

TPOs can be installed on flat and low-sloped decks, and with certain designs, the membranes can be used on high slopes -- even vertical surfaces -- and still provide a UL Class A fire rating. Most reinforced TPOs are mechanically attached (left); however, they can be fully adhered, stone or paver ballasted, or installed as a vented roofing system.

TPO roofing membranes are manufactured by either a calender or extrusion process. With either method, inherent short and long-term dimensional stability are good because plasticizers are not used in the compound. As with most single-ply membranes, a fabric reinforcement is incorporated for stability and improved puncture and tear resistance.

The polymer's inherent tensile strength achieves high ply-adhesions and welded seam strengths. When coupled with advanced mechanical fastening systems, high windstorm classifications can be attained.-- Edited by Ron Holzhauer, Managing Editor, 630-320-7139, r.holzhauer@cahners.com

Key concepts

Thermoplastic polyolefins (TPOs) combine the best attributes of today's two most popular single-ply membranes -- EPDM and PVC.

Several manufacturers offer TPO roofing, but no two membranes are exactly alike in physical properties, feel, or look.

More info

Mr. Bailie is willing to answer technical questions concerning TPO roofing. He can be reached at 877-876-7663; e-mail dmbailie@ jpscorp.com. The company web site is www.stevensroofing.com.

Extending single-ply life

All roofing materials require proper maintenance to ensure that they meet their performance standards. The following tips will help maintain single-ply systems, prolong their life, and help detect the symptoms that can cause premature roof failure.

Keep in mind, however, that while these tips are helpful, always consult and adhere to the manufacturer's guidelines and warranty.

1. Inspect the roof. Roof inspections should be conducted at least twice a year, usually late fall and early spring. Additionally, always inspect the roof after severe weather to make sure drains are clear and debris is removed. It's also a good idea to check the roof after work crews have been on the surface.

2. Review the warranty. Any self-made repairs that occur outside the warranty requirements may void the manufacturer's guarantee. In an emergency situation, perform necessary repairs according to the roofing system manufacturer's recommendations, and when possible, contact the manufacturer. Most manufacturers will help you find a suitable contractor for the permanent repairs.

3. Make a preliminary assessment. When inspecting the roof, make a preliminary assessment of the membrane's appearance, with particular attention to areas of standing water. This assessment helps identify potential problem areas.

4. Secure vulnerable spots. During the inspection, make sure the roof is properly secured to the deck. For mechanically attached and fully adhered systems, look for signs of fastener back-out (or pop-up) and insulation collapse. In both cases, fasteners are sitting above the plane of the deck, often creating a "tenting" effect. For fully adhered systems, make sure all areas are still solidly in place.

5. Make a checklist. An inspection checklist ensures all bases with respect to roof maintenance are covered. Look for deterioration, punctures, splits, separations, and/or signs of water leakage. Remember to check the following:

- Support structures

- Flashings

- Pitch pockets

- Caulk

- Fascia and roof edging materials

- Termination points.

6. Clean gutters and drains. It seems obvious, but this activity is necessary to prevent water from accumulating, backing up, and overloading the roof. As little as 4 in. of ponded water in a 10-sq ft area represents over 1 ton of dead load weight on the roof.

7. Keep accurate, detailed records. Log the results and dates of all inspections, and keep this data for future reference. It is also a good idea to take photographs of the roof during inspection to provide a good reference point for the next inspection or for warranty or insurance claims.

8. Note additions or deletions of equipment. Make sure that flashings around all rooftop penetrations are in good shape and securely fastened. If equipment has been added since the roof was installed, make sure the flashings were installed with the same materials and techniques used for the roofing. Also ensure that the work was done by an authorized contractor.

9. Keep foot traffic to a minimum. Foot traffic can cause membrane system problems. Damage is prevented by installing walkway pads or pavers in areas of heavy traffic.

10. Notify the manufacturer of intended alterations. Always notify the manufacturer of any intended alterations or changes to the roofing system.





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